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• why this template function fails to compile? - 2 Updates

why this template function fails to compile?

quanzhou <anhonghe@gmail.com>: Apr 11 10:03AM -0700 #include <concepts>   struct Callback{}; template<typename... Args, std::invocable<Args..., Callback> Func> void reg(Func) { } int main() { // good reg<double, char>([](double, char, Callback) -> void { }); // bad reg([](double, char, Callback) { }); return 0; }   Tried g++-11, error as following:   /usr/include/c++/11/concepts: In substitution of 'template<class ... Args, class Func> requires invocable<Func, Args ..., Callback> void reg(Func) [with Args = {}; Func = main()::<lambda(double, char, Callback)>]'   See Args get as {} while Func is correct. What I would like is Args to be {double, char}, why I need to explicitly provide it?   Thanks all you experts.

quanzhou <anhonghe@gmail.com>: Apr 11 10:18AM -0700 I need this Args... type deduction in reg() function because I'm gonna forward it.   在 2023年4月11日星期二 UTC-7 10:03:21，<quanzhou> 写道：

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